Method of cementing wells



. h INVENTOR. Ome M Manes M ATTORNEYS.

O. N. MANESS METHOD 0F CEMENTING WELLS Filed Jan. 9, 1939 @c 2g, i940.

Patented Oct. 29, 1940 UNITED STATES PATENT oFFlcE MIETHOD OF CEMENTING WELLS Orie N. Maness, Long Beach, Calif., assignor to The Dow Chemical Company, Midland, Mich., a corporation of Michigan The invention relates to methods of cementing wells and yconcerns an improved method of placing Ia cementitious sealing material behind a perfora-te liner in a well bore. It more particularly concerns an improved method of cementing perforate liners whereby cement or the like may be displaced from within a perforate liner into the annular space between it and the kwell bore at any `desired level therein so vas to seal olf only a selected portion of the space behind the li-ner.

In wells, such as for example oil wells, having their producing zone or zones located in formations such as sands which are of a loose or unconsolidated nature, ilt is necessary in order to satisfactorily produce the well `to line the well bore over Aa portion of its depth with a metal liner or screen. This metal liner is perforated or slotted in such .a manner as to prevent particles of the formation from being carried into the well along with the mineral fluids, for other- W-ise the particles en-tering the well cut or abrade the valves and other parts of the pump ordinarily used to lift the mineral fluid to the earths surface. In addition to preventing particles from 'Y entering the well and damaging the equipment therein, the perforate metal liner prevents the walls of the well bore from caving.

It oftentimes happens that as such wells are produced through the perforate liner, it becomes desirable, and in some instances necessary, to seal off a zone or section of the formation at a point not necessarily at the bottom of the well in order to exc-lude undesirable fluids from the well. For example, water may be owing into an oil Well through the liner at Ia point some vdistance above the oil-producing stratum and it is usually desirable to exclude such water without shutting off the flow of oil into the well.

Although cement and similar materials have been used for Various sealing operations in wells, their use in connection with sealing off a particular zone behind a perforate liner generally gives unsatisfactory results. This is because it is difcult, if not impossible, by any of the methods known in the ar-t to effectively displace the sealing material from inside the lliner and place it at the desired location in the well bore exterior of the metal liner. If cement grout or a similar material is to |be used to seal off a particular stratum or section behind a perforate liner, it is necessary that the sealing material .be introduced into the well inside the liner and be just displaced therefrom in such a manner as to completely ll the annular space .between the perforate liner and the well bore over that section of the formation it is desired to seal, for otherwise an effective seal is not generally produced. In

addition, if the sealing vagent is not completely displaced, it may solidify inside the liner and must Ibe drilled out before the well can be produced.

I have discovered that by first introducing into the well a non-penetrating liquid mixture in an amount sucient to lill the well including the annular space .between the liner and the well 10 metal liner into the space .between it and the well bore. In those instances where it is desired to introduce Ithe sealing agentlbehind the perforate Iliner adjacent the bottom of the Well, the rst step above mentioned may be omitted, the

sealing material Ibeing first introduced and then displaced from inside fthe liner by use of a nonpenetrating liquid mixture containing a suitable filler.

The term non-penetrating liquid mixture used herein and in the appended claims means a liquid mixture comprising a dispersion or solution in a liquid of a material which prevents the liquid from penetrating porous formations such as those -traversed by a well bore but of suflicient fluidity to be introduced into the well and readily 85 withdrawn therefrom.

In .the foregoing manner, cement grout or other similar sealing materials may be directed into the space between the liner and the well bore at any desired level in the Well vbore and in such a manner .that the sealing materialfcompletely fills the space Ibetween the liner and the well bore over -any desired section, thus forming a highly effective seal between liner and Well bore.

The accompanyingdrawing, forming a part of this specification and which' illustrates a mode of carrying out the invention, is -adiagrammatic vertical view partly in section'of an oil well.

In the drawing, the upper portion I of the Well is cased land passes through non-productive earth and rock, the casing 2 being provided with casing seat 3 cemented in the rock stratum 4. The Ilower uncased por-tion 5 of .the well passes through an impervious stratum 6, a gas stratum 1, a water-bearing stratum ll,l and kterminates in 011-,55

bearing stratum 9. The lower portion 5 of the well is shown provided with a slotted type of perforate metal liner I0, the slots being indicated by numerals 3l. The liner extends over the entire uncased portion of the bore hole,`i. e., from the bottom 28 up into the casing 2 to a point II, for example. A releasable packer I2 of conventional type, such as a hook-wall packer, positioned for a treatment according to :the invention is shown attached to thejlower end of the tubing I3 from which the pump assembly has been removed. lThe packer I2 is shown seated at the lower level I1 of ythe gas-bearing stratum 'l sealing the annular space 29 between -the -liner I and tubing I3. The annular space 30 between the liner and the well bore below level I5 is shown iilled with a non-penetrating liquid mixture. The lower portion of the Well linteri-orly of the liner is shown iilled with a non-penetrating liquid mixture I8 containing a ller up to a point I5, a short distance below the lower level of the water-.bearing stratum 8. Cement grout IB is shown displaced into the annular space outside the perforate liner and filling said annular space from level I5 up -to a point I'l a short distance above the upper level of the water stratum 8. Non-penetrating liquid mixture containing la ller and designated by numeral I8 is shown filling the space inside the liner above rthe level I5 and a portion of the tubing up to point I9. The remainder of the tubing above the level I9 is shown iilled with -a liquid such as oil which is used as a pressuring medium on top of thenon-penetrating liquid mixture containing the iiller. Above fthe ground level the casing head 2I, through which the .tubing I3 extends into the Well, is Ishown equipped with pipe 22 communicating with the casing, said pipe being provided with valve 23. To the tubing I3 above the casing head pipes 24 and 25 controlled by valves 26 and 21, respectively, are connected, suitably 4arranged for carrying out the method according to the invention and for producing the Well.

In accordance with the invention, a sealing operation employing a neat cement slurry may be carried out in the following manner where it is desired that the sealing material be directed into only a certain zone or section of the annular space` between the liner and the well bore such as, for example, the section opposite the water-bearing stratum 8. With the releas'able packer I2 attached to the tubing I 3held in a seated position so as to form a seal between the tubing and liner at level II, a quantity of nonpenetrating liquid mixture designated by numeral I 4 is introduced into the well through the tubing I3 in an amount sufflcient to iill the annular space exterior of the liner up to a point I5 Just below thelower level of the water-bearing stratum 8. The quantity of non-penetrating liquid mixture required may be readily calculated from a lmowledge of the diameter of the liner, the size of the well bore, and the location of the water-bearing stratum. A quantity of non-penetrating liquid mixture containing a ller and designated by numeral I8 in an amount calculated to iill the interior of the liner up to a level I5 is then introduced into the liner and pressure applied thereto displacing the non-penetrating liquid mixture iirst introduced into the annular space exteriorly of the liner into theposition shown in the figure. A quantity of a neat cement slurry in an amount sumcient to fill the annular space outside the liner between the levels I5 and Il is introduced into the well and the iiller.

allowed to come to r'est on top of the column of the non-penetrating liquid mixture containing Thereafter a quantity of a non-penetrating liquid mixture containing a filler is introduced into the well in an amount suilicient to iill the interior of the liner above the level I5 and a portion of the tubing and pressure applied thereto by pumping oil indicated by numeral 20 into th'e tubing I3. The'non-penetrating liquid mixture containing the iiller under the pressure thus applied thereto acts to displace Athe cement slurry through the perforate liner without itself passing through the same perforations because the ller in the mixture coats the perforations thus sealing them against the passage of fluid. An abrupt rise in the pressure applied to displace the cement slurry indicates that the cement is entirely displaced from the liner and that the iiller contained in the non-penetrating liquid mixture has sealed the perforations. The ease and completeness with which the perforations or slots in the liner are sealed by the filler contained in the non-penetrating liquid mixture depends of course, upon the size of the perforations. In commercially available liners the diameter of the perforations, or in those cases where a slotted liner is used, the width of the slots generally varies from between about .005 to .04 inch, although liners having perforations or slots of other sizes may be employed. Pressure is preferably held upon the non-penetrating liquid mixture until the cement sets, after which the packer may be re1eased,the well bailed or otherwise cleaned out, and returned to production.

Although the method has been described with particular reference to placing a cementing material in a selected portion of the annular space between a well bore and aliner above the bottom of the well bore, it is to be understood that the method may be suitably used to displace a cementing material'from other portions of the liner such as the lower portion of the liner by introducing the -desired quantity of cementing material/into the liner and thereafter displacing it therefrom by applying pressure upon a nonpenetrating liquid mixture containing a filler introduced into the liner or top of the cementing material.4

Various other modifications of the method just described may be'employed. For example, instead of iilling the lower portion of the well bore with a quantity of non-penetrating liquid mixture in order to control the level at which the sealing or cementing material is to be displaced, a packer of any conventional type, such as a ce-y ment retainer, may be set at the lower level at which it is desired to produce the seal, or the liner may be bridged over at the desired level in the conventional manner. In many instances the use of a packer attached to the tubing may be dispensed with and pressure applied directly on the top of a column of non-penetrating liquid mixture containing a ller. In some instances it may be desirable to insure against any of the cementing material returning through the perforations in the liner into the annular space between the liner and the tubing above the packer if such be used. To prevent such return oi.' the cementing material, a quantity of non-penetrating liquid mixture containing a iiller may be introdced into the annular space between the tubing and liner above the packer'and pressure sealing material into the interior of the liner above the packerwhile the sealing material is being displaced from the liner below the packer.

sists of a solution or dispersion of an organic in water. By an organic jellifying material is meant an organic material capable of being dispersed or dissolved in water to -make a mobile liquid dispersion of solution, which liquid exhibits jellifying characteristics after a time. Suitable organic jellifying materials may be prepared from starches such as those of cassava or rice by mixing them with water to form a thin paste and boiling the mixture until the starch is hydrolyzed. The cooked starch is dried at about 80 C. and the dried material ground preferably to a iine powder. The powder so produced may be mixed with water in a concentartion of from about 1 to 8 per cent by weight to give a dispersion or solution which possesses suitable non-penetrating characteris- Still another type of non-penetrating liquid mixture may be made by mixing a material such as bentonite with water in amounts of between about 1 to 5 per cent by weight. Such mixtures do not substantially penetrate into relatively porous formations, but readily pass through the perforations or slots in the metal jellifying material liner and act to confine the sealing material to the desired level in the well bore.

Illustrative examples of iillers suitable to add to the above non-penetrating liquid mixtures to produce a mixture which is capable of displacing the cementing material through the relatively small perforations or slots in the liner without itself passing through the perforations are cellophane scraps, mica flakes, shredded photographic lm scraps, hemp fibers, and the like. Cellophane scraps in the form of confetti-like particles are preferably used because reverse flow of fluids at moderate pressure through the liner readily clears the perforations or slots so that permanent plugging of the slots does not occur. If desired, fillers having similar characteristics and which may be readily removed by suitable solvents in case plugging does occur may be employed. Illustrative examples of soluble fillers of a resin-like nature are styrene scraps, ethyl cellulose scraps, and cellulose acetate iilm scraps. Styrene and ethyl cellulose are readily soluble in benzene or toluene, while cellulose acetate is readily soluble in acetone. The amount of such i'lllers to add to the non-penetrating liquid mixture to give the most satisfactory results is from about 1 to 5 per cent or more by weight, and preferably about 3 per cent.

Sealing agents which may be suitably used according to the method of the invention are those of a fluid nature capable of passing through the perforations in the liner which of themselves spontaneously solidify to form a strong solid mass. Although conventional neat cement slurries are preferably used as sealing agents, mobile resin-forming liquids of the type which are of themselves capable of transformation into a solid resin after a time by polymerization, addition, condensation, or like chemical reaction may be suitably employed in similar manner.

The following are illustrative examples of such resin-forming liquids:

Example 1 Mix together 70 parts of liquid vinylidene chloride and 30 parts of hexachlordiphenyloxide. When ready for use, add a catalyst mixture of benzoyl peroxide and lead tetraethyl, a suitable amount being' 0.5 per cent of benzoyl peroxide and 0.5 per cent lead tetraethyl, based upon the volume of vinylidene chloride in the mixture. This resin-forming liquid becomes non-fluid in 2 hours at 110 F. and solid in about 6 hours.

Example 2 A dilute solution of sodium silicate is prepared by diluting 40 per cent commercial sodium silicate (Na2O-3.22Si02) with water to a speciiic gravity of 1.171, giving a solution containing 19.1 per cent by Weight of sodium silicate. The dilute solution of sodium silicate so prepared is then added with vigorous stirring to a dilute solution of hydrochloric acid prepared by adding water to concentrated (37 per cent by Weight) hydrochloric acid in the following proportions by volume:

Per cent -by volume Dilute solution of sodium silicate (19.1%

by weight NazO-3.22SiO2) 1 0-75 Concentrated hydrochloric acid (37% by by weight) 10-20 Water 12-70 Liquid silicate mixtures having a composition within the range of the above proportions spontaneously become solid gels in from 95 to 25 hours at 120 F. depending on the proportion o! each ingredient.

Example 4 A dilute solution of sodium silicate is prepared by diluting 40 per cent sodium silicate NazO-3.22S02) with water to the specific gravity of 1.171, giving a solution containing 19.1 per cent by weight of sodium silicate. The dilute solution of sodium silicate so prepared is then added with stirring to a solution of ammonium bicarbonate, prepared by diluting with water a stock aqueous solution of ammonium bicarbonate containing 16.9 per cent by weight of the carbonate in the following proportions by volume:

\ Per cent by volume Dilute solution of sodium silicate (19.1%

by weight NazO3.22SiOz) 5-85 Aqueous ammonium bicarbonate solution 5-85 Water 0-85 Liquid silicate mixtures having a composition within the range of the above proportions spontaneously become solid gels in from 1/2 to 15 hours at F., depending upon the proportion of each ingredient.

Among the advantages of the invention are that a sealing material can be readily and completely displaced from the interior of a perforate liner, thus eliminating the possibility of forming a plug inside 'of the liner; that a sealing material can be displaced from the interior of a perforate liner in such a manner as to completely ll the annular space between the well bore and the liner, insuringan eiective seal being formed; and that a sealing material can be directed into the annular space between the perforate liner and the well bore at any desired level so that the annular space between any two levels may be selectively sealed off.

Other modes of applying the principle of my invention may be employed instead of those explained, change being made as regards the method herein disclosed, provided the step or steps stated by any of the following claims or the equivalent of such stated step or steps be employed.

I therefore particularly point out and distinctly claim as my invention:

1. In a method of producing a seal in the annular space between a well bore and a perforate liner therein, the steps which consist in introducing the sealing material into the perforate liner, then introducing into the perforate liner on top of the sealing material a non-penetrating liquid mixture containing a filler capable of preventing the non-penetrating liquid mixture from passing through the perforations in the liner', and applying pressure upon said non-penetrating liquid mixture so as to displace the sealing material from the perforate liner.

2. In a method of displacing a sealing material from a perforate liner or the like located in a well bore into a selected section of the annular space between the perforate liner and the well bore, the steps which consist in introducing into the perforate liner a quantity of non-penetrating liquid mixture in an amount suflcient to ll the annular space outside the perforate liner up to the lower level of the Zone to be sealed, introducing into the liner a non-penetratingr liquid mixture containing a ller in an amount equal to the volume of the liner between the bottom of the liner and the lower level of the zone to be sealed, introducing the sealing material into the perforate liner; introducing into the perforate liner a yquantity of non-penetrating liquid mixture containing a filler capable ot preventing the nonpenetrating liquid mixture from' passing through the perforations in the perforate liner, and applying pressure upon the non-penetrating liquid mixture containing the lle whereby the sealing material is just displaced from inside the perforate liner and confined in the annular space outside the perforate hner above the level of the non-penetrating liquid mixture in said annular space.

3. In a method of displacing a sealing material from a perforate liner or the like located in a well bore into a selected Zone of the annular space between it and the perforate liner, the steps which consist in temporarily sealing ofi' the interior of the liner at the lower level ofthe zone to be sealed, introducing a sealing material into the perforate liner, introducing into the perforate liner a quantity of non-penetrating liquid mixture containing a filler capable of preventing the nonpenetrating liquid mixture from passing through the perforations in the perforate liner, and applying pressure upon the non-penetrating liquid mixture containing the filler so as to displace the sealing material from the perforate liner.

4. In a method of displacing a sealing material from a perforate liner or the like located in a well bore into a selected zone o'f the annular space between the perforate liner and the well bore, the well being equipped with the usual casing and tubing, the steps which consist in temporarily sealing off vthe interior of the liner at the lower level of the zone to be sealed, setting a packer attached to the tubing above the upper level of the zone to be sealed so as to form a seal between the tubing and the perforate liner, introducing into the annular space between the tubing and the perforate liner a quantity of non-penetrating sesl liquid mixture containing a filler, introducing a i sealing material into the perforate liner, introducing into the perforate liner a quantity of nonpenetrating liquid mixture containing a ller capable of preventing the non-penetrating liquid mixture from passing through the perforations in the liner, and applying pressure upon the nonpenetrating liquid mixtures containing the filler, whereby the sealing material is displaced from the perforate liner into the annular space exterior of the liner and confined in said space.

ORlE N. MANESS. 

